Conventional helical products such as dead-ends and insulator ties typically consist of sets of wire strands. After the individual strands are formed, they are spiralled and then glued together to form the stranded sets. In many cases grit is then sprayed onto the glued sets to raise their collective coefficient of friction, and portions of each set are thereafter straightened as appropriate to produce the resulting product. This straightening technique can cause the glued strands to detach, however, and the overall forming process is often labor intensive.
U.S. Pat. No. 3,847,491 ("the '491 patent") to Poffenberger discloses other helically preformed dead-ends and "splice-type" appliances for cable and wire installations. According to the '491 patent, the dead-ends may be constructed of either plastic rods or a flat ribbon or strip of material such as steel. Following separate formation of the two helical legs and a U-shaped bight of each dead-end, the three elements are joined by welding or clamping them together. The dead-ends may also contain knurled or gritted surfaces to enhance their ability to grip cables, although no mechanism for knurling the appropriate surfaces is disclosed in either the '491 patent or in U.S. Pat. No. 3,183,658 to which it refers.
U.S. Pat. No. 3,800,397 ("the '397 patent"), also to Poffenberger, addresses a method for making the helical legs and bight of the dead-end. As stated therein, each leg is created by forming an elongated helical strip and then cutting the strip to the desired length. Another continuous strip is formed into "continuous generally sine wave type undulations," with "each individual undulation corresponding to the desired configuration" of the bight of the resulting dead-end. The undulating strip is cut to define multiple bights, one of which may then be joined to the helical legs as noted above to create the dead-end.
As discussed in the '491 and '397 patents, the pitch lengths of the two helical legs differ. In use, the first leg (having longer pitch) is wrapped about a cable, with the second leg thereafter wrapped about both the cable and the first leg. The helixes of the first leg purportedly provide a body of a relatively uniform and more rigid contour for the helixes of the second leg to grip, while the second leg is intended to clamp the surface of the first leg tightly about the cable.
Neither the '491 patent nor the '397 patent contemplates manufacturing both the helical and bight portions of dead-ends from a continuous strip of material. Similarly, neither patent discloses forming other appliances useful in connection with cable installations or any mechanism for knurling such appliances in-line. The '491 and '397 patents additionally neither teach nor suggest devices having legs of equal pitch length, each intended to wrap around a conductor or other cable. Instead, as discussed therein, the leg of the dead-end of the '491 and '397 patents having the shorter pitch is wrapped around the other leg to diminish excessive localized radial pressures that otherwise purportedly would occur.